2012 Annual Report
1a.Objectives (from AD-416):
1. Develop and validate diagnostic tests for the viruses involved in these complexes and transfer these validated tests to interested parties; 2. Identify candidate virus vectors based on virus genomics with greenhouse transmission testing; 3. Identify virus combinations capable of causing severe disease outbreaks, and; 4. Evaluate virus and vector resistance in Rubus germplasm; conduct field transmission tests to determine when viruses are being spread in the field and implement targeted control based on vector biology for management of the diseases. 5. Communicate the results: Outreach, Education and Implementation for growers, extension agents, and agricultural consultants.
1b.Approach (from AD-416):
This project aims to minimize or eliminate the impact of virus complexes in production fields through minimal pest management targeting the virus/vector combinations easiest to control, this includes the improvement of virus testing in certification programs.
Research in this project has focused on mixed virus infections in red raspberry in the Pacific Northwest and how each virus in the mixed infection contributes to severe crumbly fruit and reduced plant growth. Interactions between three viruses are being studied, Raspberry bushy dwarf virus (RBDV), Raspberry leaf mottle virus (RLMV) and Raspberry latent virus (RpLV). Surprisingly, when RBDV is present in mixed infections with RLMV, the amount of RBDV increases approximately 400-fold. The amount of RLMV and RpLV was not affected in mixed infections and RBDV was not affected by RpLV. Field plots were established in 2010 that had all combinations of the three viruses as well as individual infections and healthy plants, for a total of eight treatments: Healthy, RBDV, RLMV, RpLV, RBDV + RLMV, RBDV + RpLV, RLMV + RpLV, and RBDV + RLMV + RpLV. During the establishment year, 2010, the combinations of RBDV + RLMV, RBDV + RLMV + RpLV had the greatest impact on plant growth. In the first fruiting year, these two combinations continued to have the greatest impact on plant growth. However, the RBDV + RpLV and RBDV + RpLV + RLMV plots had the greatest impact on fruit quality. The trials are continuing for one additional year. After the first two years, it appears that the RBDV + RLMV combination had the greatest impact on plant growth and that RBDV + RpLV had the greatest impact on fruit quality. Understanding the interactions between the viruses will allow us to target the weakest link in complex rather than trying to manage all three viruses. RBDV is pollen-borne and controlling pollen movement results in poor fruit set, thus, the cure can be as severe as the disease. The other two viruses are aphid-transmitted and potentially controlled with a single insecticide spray that is timed to the peak aphid flight, which occurs in mid- to late-June. This research was conducted in support of objective 3B of the parent project.